Endocrine Abstracts

Aim: To define a basal Cortisol threshold that could potentially predict the outcome of short synacthen test (SST) and thus reduce the need for performing SST in patients with low clinical probability for adrenal insufficiency.

Methods: We analysed SSTs done at our hospital in non-critically ill general medical and endocrine patients, who had abnormal 0900 h Cortisol levels (n=110, male-45, female-65) between January 2016 to March 2016. The SST was considered pass when the 30 min Cortisol was 480 nmol/l and above as per our local laboratory protocol.

Findings: Of the 110 patients, 84 passed the SST (76%) and 23 (24%) had failed the SST. Majority of the SSTs were done between 0900 and 1100 h in the morning. All patients with a basal 0900 h Cortisol <100 nmol/l had failed the SST. Among patients with a basal 0900 h Cortisol of 350 nmol/l and above, 88.9% had passed the test. All patients with a basal 0900 h Cortisol level of 400 or above had passed the SST.

Conclusion: If the 0900 h Cortisol is less than 100 nmol/l, then there is no need to perform SST as all of them will fail. A 0900 h Cortisol level above 400 nmol/l predicts a satisfactory pass on the SST. A Cortisol level above 350 nmol/l highly predicts having a normal SST. Basal cortisol levels between 100 and 350 nmol/l should have an SST to confirm hypoadrenalism. A 0900 h baseline serum may help in avoiding unnecessary SST and provides a cost-effective approach.